✨ Supports -s and -l to specify starting point and length in seconds to be rendered. (for making a preview, etc.)

[5argon]

A feature to prepare for newer BMS players that supports pre-rendered preview e.g. beatoraja

Problems : libsndfile produces a .wav with bad header. The file plays correctly in audio player but beatoraja 0.5.1 plays the preview with high frequency artifacts. sox output.wav output2.wav fixes the problem and sox will says sox WARN wav: wave header missing extended part of fmt chunk.

[5argon]

Now it seems beatoraja can play the preview file with sox WARN wav: wave header missing extended part of fmt chunk properly, but to fix the header anyways it is because libsndfile outputs a wav file that does not have an extended part.

According to this website non-PCM must have an extended part. We are using an IEEE floating format 03 but libsndfile outputs a file with fmt chunk size as 16, meaning that it won't have a room for extension size field cbSize which can be 00 00 but must be present. We can change the chunk size to 18, add the cbSize field as 00 00, and finally add +2 to the overall chunk size with codes like this.

  let outWav = fs.readFileSync(outfilepath) // Read back the output from libsndfile

  const chunkSize = outWav.readInt32LE(4)
  outWav.writeInt32LE(chunkSize + 2, 4) // Increase overall size by 2 bytes for the extension field
  outWav.writeInt32LE(18, 16) // To add extension field chunk size should be 18. It is on position 16

  let modifiedWav = Buffer.alloc(outWav.length + 2) // Initialize as all 0
  outWav.copy(modifiedWav,0,0,36) // Stops at before extension size (cbSize)
  outWav.copy(modifiedWav,38,36) // Left the extension field as 00 00 and copy the rest
  fs.writeFileSync(outfilepath,modifiedWav);